The present invention is generally directed to a medical diagnostic apparatus, and more particularly to a combination electronic communication and medical diagnostic apparatus which can be used as an electronic communication device, such as a beeper/pager or cellular phone, as well as a medical tool to detect and/or monitor neuropathy.
Diabetes is a very common disease that often leads to painful neuropathy. Symptomatic diabetic neuropathy is preceded by an asymptomatic phase during which nerve conduction by the large fibers is impaired, leading to an impairment of vibration perception. Vibration threshold is a continuous measure and by necessity, categorization into a binary outcome will mean setting of an arbitrary threshold. The 95th and 97th percentiles in non-diabetic populations have previously been used as thresholds for neuropathy. Vibration threshold is the most valid measure of nerve function in diabetic patients and has been used as a gold standard.
Vibration testing has long existed in various manners. For example, vibration threshold testing devices are currently being used which include two fixed probes in one or two boxes which are placed on a table or floor. The patient must touch them with the fingers or toes and indicate which one is vibrating. A further vibrating tool known as Biothesiometer, which is similar to vibrating devices sold in adult paraphernalia shops, is applied to an extremity and the vibration level is turned up until the patient can feel the vibration. The level is then read off a meter. These devices have also been computer driven.
A further example of vibration testing is by the utilization of a tuning fork, which can be applied to an extremity. A vibrating pen for detecting nerve impairment (neuropathy) is disclosed by Laudadio in U.S. Pat. No. 5,931,793. However, this is merely a pen-like device that does not incorporate the function of a beeper/pager or cellular phone. Furthermore, Laudadio's pen-like device measures vibration threshold as a binary outcome requiring setting of arbitrary thresholds used to define the severity of neuropathy as mild, moderate or severe.
A vibrating pen marketed by Solarwide Inc. sends a signal to indicate that the user has a call on a cellular phone but its use for the detection of neuropathy has not been described. Another form of vibrating pen known as a Wiggle Writer for children is disclosed in U.S. Pat. No. 5,208,987, which operates on a similar principle using an offset motor which causes the pen tip to draw circles.
A quantitative assessment of vibration threshold over a wide range of frequencies using various vibratory amplitude levels at vibration frequency is disclosed by Lacourse and McCoy in U.S. Pat. No. 5,002,065, in which they show that an increase in the perception threshold for vibration is the earliest detectable objective sign of carpal tunnel syndrome. Lee et al. have demonstrated the usefulness of determining vibration perception threshold in patients with end-stage renal disease as a measure of neuropathy (Kidney International, Vol 64, pp. 1089-1094, 2003). There are several other medical conditions, including alcohol abuse and vitamin deficiencies, that are associated with neuropathy.
Loss of large myelinated fibres is the most constant morphologic feature of neuropathy in patients with kidney failure or uremia. Impaired vibration perception of the toes is early and initially the only clinical sign of this peripheral neuropathy (G. Said, L. Boudier, J. Silva, J. Zingraff, T. Druecke: Different patterns of uremic polyneuropathy:clinicopathologic study. Neurology 33:567-574, 1983) and measurement of vibratory perception thresholds is more suitable to evaluate progression or recovery of uremic neuropathy than is measurement of nerve conduction velocity (Said et al, Id., and F G I Jennekens, E J Dorhout Mees, D Van der Most van spijk: Uremic polyneuropathy. Nephron 8: 414-426, 1971).
Although vibration threshold has been recognized as the gold standard for diabetic neuropathy, the investigators have been testing alternative measures as surrogates for the diagnosis of neuropathy (Rahman et al., Diabetic Medicine 20: 368-374, 2003), because the currently available devices used to determine vibration threshold are cumbersome, mostly used as research tools, and are not widely available in the primary care setting. In fact, majority of physicians, including the inventor of this invention have never seen the vibrameter devices, let alone use it.
In common clinical practice, the current standard of medical care is to use tuning fork as qualitative, or at best semiquantitative tool, for diagnosing neuropathy. However, tuning forks are cumbersome, inaccurate, operator-dependent and consequently are used infrequently and only by a small minority of physicians. In addition, in using a tuning fork, physicians tend to underestimate or overestimate the loss of vibration sensation. In diabetic patients tuning fork overestimates loss of vibration, compared with quantitative vibration threshold using a vibrameter (T M Burns, A Taly, O'Brien, P J Dyck: Clinical versus quantitative vibration assessment: improving clinical performance. Journal of the Peripheral Nervous System 7:112-117, 2002). On the other hand, in uremic patients, tuning fork examination could demonstrate abnormalities in only 2.5% of patients whereas vibrameter was much more sensitive, detecting abnormalities in 47.5% of patients, similar to the 45% using nerve conduction velocity as the gold standard (M J Hilz, P Zimmermann, G Rosl, W Scheidler, J braun, B Stemper, B Neundorfer: Acta Neurol Scand. 92(6):486-90, 1995). Similarly, in the same study, in alcoholic patients tuning fork revealed abnormalities in only about 15% compared to 60% by vibrameter and about 35% by nerve conduction velocity. Therefore, it is evident that use of tuning fork is inaccurate and inadequate as a clinical tool for the detection of neuropathy in diabetic, uremic or alcoholic patients. On the other hand, vibrameter is more sensitive and specific for the detection of neuropathy since it employs quantitative stimuli, a broad range of stimulus magnitudes and null stimuli.
None of the diagnostic or monitoring devices described above, however, serve as electronic communication devices, either, for example, as a receiving pager or a cellular phone.
In view of the drawbacks associated with conventional tools and techniques, there is a need for a better and improved clinical tool for the detection and/or monitoring of neuropathy that is portable, can be easily carried by a physician or other health care professional on their person, and is more sensitive and specific compared to the tuning fork.